<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/62016>62016</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            llvm-link some bitcodes compiled with "-O0 -Xclang -disable-O0-optnone" failed
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          tr4v3ler
      </td>
    </tr>
</table>

<pre>
    I am working on a program analysis project and my target is the bitcodes of some modules, which are linked together by llvm-link from some individual bitcode. Because I want to minimize the optimization during the compilation process to avoid affecting my analysis process, I use the "-O0" option. In order to optimize the linked bitcode with mem2reg in the future, I added "-Xclang -disable-O0-optnone" to compile the individual bitcode. However, many errors occurred during the llvm-link process, which would not happen without the "-Xclang -disable-O0-optnone" option. Is there any way to preserve the "-O0" option during the compilation process, successfully complete the llvm-link step, and perform mem2reg optimization afterwards? One method I already know is to manually remove the optnone attribute from the bitcode, but I do not like using this method. Is there any better way? By the way, I am using the legacy pass.

```
# case one: no error, but mem2reg is not effective
clang -O0 -emit-llvm -S demo1.c -o demo1.ll
clang -O0 -emit-llvm -S demo2.c -o demo2.ll
llvm-link -S demo1.ll demo2.ll -o demo.ll
opt -mem2reg -S demo.ll -o target.ll

# case two: many errors during llvm-link
clang -O0 -Xclang -disable-O0-optnone -emit-llvm -S demo1.c -o demo1.ll
clang -O0 -Xclang -disable-O0-optnone -emit-llvm -S demo2.c -o demo2.ll
llvm-link -S demo1.ll demo2.ll -o demo.ll
opt -mem2reg -S demo.ll -o target.ll
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJy8VU1vpEYQ_TXMpcSIaebzwGGd1Sg--ZBLrg1dQMfdXag_BpFfHxVg7HU2u0oOkSwPoPp479XrahmC7hxilZ2estPXnUyxJ19Ff3yUBv2uJjVVzyAtjORfteuAHEgYPHVeWpBOminowB_-wCaCdArsBFH6DiPoALFHqHVsSGEAaiGQRbCkksGQiV9g7HXTg_QIRrtXVBCpw9ijh3oCYx425-_QerJLrnZKP7RK0rzV3cMTNjIFhGcYpYsQCax22uo_ce5PQ-QXGTU5UMkzDf7ekB20WT4PnhoMgXPlg7QC2bbYRA610zc8OYyRPwO35DqZEPlLkQkxdyK3h2cH5BV6Lrd2X0JXkityGHXswaIVHjvQbg5pU0welw5SKVRz_d8bI10HudJB1gbzlyKnITpyyH0jrWSWLt_T6Fca8YGe61rpJkDvyQegpkneo_qoy7vsH-gugxopGQWOIvRyGNDNDCjFTYcf49z0mY3hERjJKCcmMHgM6B_fl_QnY2OAITX82CZjpjnGYMRPfELEgWPZpgP6lrzd5P_GJbKN6EfpVcjKO7w4BIuxJ8UzMR6lmuDV0Tg7nFjQJLmtR0uPzXTMGmSMXtcp4uLhD-eBgdQpwjMomiU1-hUhhYWnDmvLT2rVGCN6Fo2RPU1zRX5bDGO3AggGO9lMMMgQ9lnxNSu-rP_Pxfq3vIoSGhkQeEjlF3C0mOMN3-bPMKPE5WA8cMle5_1SQI5Wx5zFhvw3UGjpsG8gp_XRmJ8niPcEsSW8j28ra8wW8xa_hdMQIX_DvGasccta2iI_0Y8jMf2Pp2N13Ybgbwz-2e7_QY5_Vex_lurNMjtVlepW3uQOq8P5WtxOV1Fedn0lT7dbfZGX060V4lI014Nqrpe6bkV7xtv1vNOVKERZHIvrQZyK8rI_S4HHBg_nS3MqbpdjdizQSm32zGJPvtvpEBJWZ1EczjsjazRhvqeEcMhHLyReKnxt-WpmXqcuZMfC6BDDe5Woo8HqwxLga2S7k9a9qZZdvOydH42Cd1IrOWOXvKn6GIeQlV8ycc_EvdOxT_W-IZuJO3dcf_L1fszEfYYdMnGfaf0VAAD__xdrh8Q">